Keyboards are indispensible devices for people when using computers nowadays. There are many keys on a keyboard, for being pressed by a user so as to input instructions. As shown in FIG. 1, the structure of a conventional keyboard 9 includes a keypad 91, a circuit board 92, and a plurality of keys 93. The keys 93 correspondingly pass through a plurality of through-holes of the keypad 91, to be connected to the circuit board 92, for being pressed by a user.
However, due to the tolerance of and the materials used in a manufacturing process for each key 93 and the keypad 91, it is easy for dusts/liquids to float into/penetrate into gaps (positions of the through-holes) between the key 93 and the keypad 91, and then stay above the circuit board 92, which may seriously interfere a circuit/light-path of the key 93, and generate signal misjudgement because of incapability of accurately transmitting a signal, thereby influencing the precision. Furthermore, the dusts/liquids fall onto the circuit board 92, which may cause poor contact or even damage of the circuit board 92. Therefore, the conventional keyboards still need to be improved.